SELECT COUNT(*), "CLIENT_TABLE"."AGE"
FROM "CLIENT_TABLE"
GROUP BY "CLIENT_TABLE"."AGE"
ORDER BY "CLIENT_TABLE"."AGE"

CASE
    WHEN "CLIENT_TABLE"."AGE" < 18 THEN 'Under 18'
    WHEN "CLIENT_TABLE"."AGE" > 18 AND <= 21 THEN '19 - 21'
    WHEN "CLIENT_TABLE"."AGE" > 21 AND <= 35 THEN '22 - 35'
END AS Age